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I need help to know how the Aux port on the ASCO sol.vlv model EV8316304 or similar, I mean the Sol.Vlv which used Aux port as external or Internal piloting how it's functioning and is there any relation between the Aux port and the Cyl port

I have a case where the Aux port give the air pressure to the cylinder port when I de-energized the Normal-Close sol.vlv which I understand from ASCO manual that this piloting it's used to help the plunger incase of using the low power sol.vlv

FISHER local rep informed me that in case I want to fail safe the double action actuator to close position I must connect the the EXH port to main inst air,but this does not function at all.

The tech was on site he did trial and error way until he found that if we use the AUX port as external and we connect this AUX port to main instrument air then if we De-energized the sol.vlv the air from the AUX port it supplying the Cyl side ???????????????

please i need clarification

My E-mail: the_smart2001@hotmail.com